Laminations



H. O. BUZZELL ET AL LAMINATIONS 2 Sheet5 shee l Filed Dec.' 1o, 1965 FaG| Fl Q 5 C12 FHG,

M NENTORS BY mag'- Wl- .Iuy 9, 1968 3,391,479

H. O. BUZZELL ET AL LAMINATIONS Filed Dec. lO, l1965 2 Sheets-Sheet 2 INVENTORS ila@ d. @ci ggg BY im addof,

M ,a M

erro/mers nite States tent 3,391,479 LAM'INATONS Harold 0. Buzzeil, Woiaston, and Phoebe F. Jordan, Melrose, Mass., assignors to Poiaroid Corporation, Cambridge, Mass., a corporation ot' Deiaware Fiied Dec. it), 1965. Ser. No. 513,046 l1 Claims. (Cl. t0- 2.2)

ABSTRACT F THE DHSCLOSURE This invention relates to a novel security device for printed matter and the like.

It is one object of this invention to provide a means for protecting information-bearing surfaces.

It is another object of this invention to provide a device for protecting information-bearing surfaces from unwanted alteration.

It is another object of the present invention to provide a means for detecting unauthorized tampering with, or alteration of, informationfbearing surfaces.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the product possessing the features, properties, and relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the appended claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

FIGURE 1 represents a split-field light-polarizing device suitable for examining and analyzing larninations prepared in accordance with the instant invention;

FIG. 2 represents an identification card having laminated thereto a substantially transparent molecularly oriented overlay containing a stripe dyed with a positive dichroic dye, and a superposcd split-field light pol'arizer;

FIG. 3 represents an identification card having laminated thereto a substantially transparent imolecuiarly oriented overlay containing a stripe dyed with a negative dichroic dye, and a superposed split-field light polarizer;

FIG. 4 represents an identification card of the present invention having laminated thereto a substantially transparent moiecularly oriented overlay containing a stripe dyed with a mixture of a positive and a negative dichroic dye, and a superposed split-field light polarizer;

FIG. 5 represents an identification card having laminated thereto a substantially transparent molecularly oriented overlay containing a stripe dyed with an isotropic dye, and a superposed split-field light polarizer;

FIG. 6 represents an identication card of the present invention having laminated thereto a substantially transparent molecularly oriented overlay containing a stripe dyed with a mixture of an isotropic dye and a positive dichroic dye, and a superposed split-field light polarizer;

FIG. 7 represents an identification card of the present invention having laminated thereto a substantially transparent molecularly oriented overlay containing a stripe ice dyed with a mixture of an isotropic dye and a negative dichroic dye, and a superposed split-held light polarizer; and

FIG. 8 represents an identification card of the present invention having laminated thereto a substantially transparent molecularly oriented overlay containing a stripe dyed with a double-dichroic dye, and a superposed split-field light polarizer.

U.S. application of Robert L. Malster, Ser. No. 451,895, tiled Apr. 29, 1965, and now Patent No. 3,313,052, issued on Apr l1, 1967, describes and claims the use of a substantially transparent overlay sheet laminated to information-bearing surfaces, for example, such as identication cards, credit cards, and the like, at least'a portion of which substantially transparent overlay sheet is capa- I le of polarizing light. The resulting laminations are protected from unwanted tempering or intrusion to the extent that any attempt to do so will result in alterations in the light-polarizing characteristics of the overlay, which alterations may be readily detected by viewing the front of the lamination through a suitably oriented lightpolarizing device.

It has now been found that protected laminations of the aforementioned type can be rendered more difiicult to counterfeit, and tampering therewith or alteration thereof be made more readily ascertainable, by employing as an overlay for the information-bearing surface a substantially transparent layer, at least a portion of which is molecularly oriented and light polarizing, and which lightvpolarizing area comprises a dye or combination of dyes selected from the following categories:

(a) a mixture of a positive dichroic dye, to be defined hereinafter, and a negative dichroic dye, to be defined hereinafter, which dyes by themselves exhibit dis-- tinctiy different colors, and the mixture of which exhibits the color provided by the additive effects of the two individual components;

(b) a mixture of a positive dichroic' dye and an isotropic (nondichroic) dye, which dyes lby themselves exhibit distinctly different colors, and the mixture of which exhibits the color provided by the additive effects of the two individual components;

(c) a mixture of a negative dichroic dye and an isotropic dye, which dyes by themselves exhibit distinctly different colors, and the mixture of which exhibits the additive effects of the two individual components; and

(d) a single double-dichroic dye, to be delined hereinafter.

The term dichroism is used herein and in the claims as meaning the property of differential absorption of the components of an incident beam of light depending upon the vibration directions of the components. By dichroic dye or stain is meant a dye or stain whose molecules possess the property of showing dichroism. In the practice of the present invention, this dichroi-c property is displayed when the dyes are incorporated in molecularly oriented plastic materials in that the resulting stained areas show dichroism.

As is well known, a dichroic dye or stain has relatively, a light absorption axis and a light transmission axis, the two axes being arranged essentially at right angles to each other. Unpolarized light incident on such a substance will have a transmitted component and an absorbed component. The transmitted component will be polarizedin the plane of the transmission axis, which as indicated is located at to the absorption axis. The absorption axis of certain dichroic materials is located at an angle of 90 with respect to the absorption axis of `certain other dichoric materials when lplaced in a common matrix. This difference in the positioning of the absorption axes causes a dichroic substance to be designated as positively dichroic or negatively dicnroic in accordance with the 3 location of its absorpition axis; in other words, positive and negative dichroic substances have their absorption axes mutually perpendicular in a common matrix.

Assuming that a suitably oriented transparent plastic resinous material is dyed or stained with a dye or stain of the type described above, determination of whether the dye itself is positively or negatively dichroic may be ascertained by optical density measurements made in plane polarized light. The consideration of these measurements will lead to an understanding of the terms positively dichroic and negatively dichroic. The optical density of the stain or dye is first measured in polarized light with the orientation direction of the molecules of the plastic material parallel to the electric vector (vibration direction) of the polarized light source. This measuremerit is called d-parallel (written 1|l). A second measurenient of optical density is made in polarized light but with the direction of the molecules of the plastic material perpendicular to the electric vector. This is termed d-perpendicular (written d L). To compare the merits of positively dichroic and negatively dichroic dyes, it is convenient to always take the optical density ratio as greater than one. Thus, if the ratio di /nl is greater than one, the polarizer, and hence the dye, is given a plus sign and is called positively dichroic. On the other hand, if the ratio dl|/tl is greater than one, the polarizer, and hence the dye, is given a negative sign and is called negatively dichroic.

The present invention is based on the phenomenon that when a positive and a negative dichroic dye having different colors are mixed, e.g., in Solution, while the resulting color reflects the additive elfects of the color of each dye, neither dye loses its negative or positive character. Thus, it a suitably oriented transparent plastic niaterial is dyed or stained with a mixture of a positive dichroic stain or dye and a negative dichroic stain or dye, and the area so dyed or stained is viewed in polarized light the vibration direction of which is parallel to the orientation direction of the molecules of the plastic material, the original color of the positive dichroic dye will be observed to predominate, with the original color of the negative dichroic dye substantially eliminated, Further, if the same area is viewed in polarized light the vibration direction of which is perpendicular to the orientation direction ofthe plastic material, the original color of the negative dichroic dye will be observed to predominate,

with the original color of the positive dichroic dye sub-V stantially eliminated.

Certain single dyes or stains, hereinafter called doubledichroic dyes, have been observed to behave as both positive and negative dichroic dyes. Unpolarized light on such dyes will have two transmitted components of different wavelengths, each of which will be polarized in its respective transmission axis; the two transmission axes are mutually perpendicular. Corresponding to the two transmitted components, there are two absorbed components of different wavelegiiths, whose absorption axes are mutually perpendicular. Thus, if a suitably oriented transparent plastic material is dyed with a double dichroic dye and the area so stained is viewed in polarized light the vibration direction of which is parallel to the orientation direction of the plastic material, the color observed will correspond to the wavelength of the component whose transmission axis happens to be parallel to the orientation direction of the plastic material. If the same area is viewed in polarized light the vibration direction of which is perpendicular to the orientation direction of the plastic material, the color observed will correspond to the wavelength of the component whose transmission axis is perpendicular to the orientation direction of the plastic niaterial. When the saine area is viewed in unpolarizcd light, the color of the original dye, usually the color resulting from the additive effects of the two components, will be observed.

Substantially the suine color cllects as thoscdescribed above may be achieved by providing a mixture of an isotropic dye of one color and either a positive dichroic dye or a negative dichroic dye of a different color even though the isotropic dye itself does not break incident light into polarized components. In either case, to the naked eye, a suitably oriented transparent plastic material dyed with such a mixture will exhibit the single color produced by the additive effects of the two dyes. However, assuming the mixture is an isotropic and a positive dicnroic dye, if the area so dyed is viewed in polarized light the vibration direction of which is perpendicular to the orientation direction of the plastic material, the color of the positive dichroic dye is substantially eliminated and the color observed is substantially that of the isotropic dye alone; it" viewed in polarized light the vibration direction of which is parallel to the orientation direction of the plastic material, the color observed will be substantially the same as that of the original mixture, but somewhat darker in intensity. Conversely, if the mixture is an isotropic and a negative dichroic dye, if the area s0 dyed is viewed in polarized light the vibration direction of which is parallel to the orientation direction of the plastic material, the color of the negative dichroic dye is substantially eliminated and the color observed is Substantially that of the isotropic dye alone; if viewed in polarized light the vibration direction of which is perpendicular to the orientation direction of the plastic material, the color observed will be substantially the same as that of the original mixture, but somewhat darker in intensi-ty.

While in the foregoing description, the phenomenon of dichroisin has been discussed in relation to molecularly oriented resinous plastic sheets, it will be appreciated by those skilled in the art that certain other plastic materials, such as glass, can be suitably oriented at least superficially so as to be dyeable with negative and positive dichroic dyes; such dyed materials may be bonded to information-bearing surfaces as described herein by any Of the bonding techniques which are known to be suitable therefor. Techniques for orienting glass and thereafter dyeing or staining such glass with dichroic dyes or stains are described in U.S. Patent No. 2,400,877, issued May 28, 1946, to John F. Dreyer.

When oriented transparent sheets, at .least a portion of which are stained with any of the dye preparations aS described above, are laminated to the surface of identication cards, credit cards, or the like, a plurality of security features are conferred thereon. First, the mere fact that the overlay comprises at least in part a molecularly oriented light polarizer renders most valterations of the lamination, such as cutting and subsequent re-sealing, or heat or solvent action, readily detectable, as described in U.S. patent application Ser. No. 451,895 referred to above. Also, the dyed light-polarizing area will have -a definite hue and intensity which in and of itself renders the card distinctive. But more important, when such a card is viewed in polarized light, such as through a Silitable light-polarizing analyzing device, the colors of the individual components as described above are readily seen, these colors being different from the color of the mixture. Thus, it will be readily apparent that a card so treated is unique, in that at least a portion of its surface will be stained a distinctive color which, while appearing to the naked eye to be a single color, is readily resolved into two different colors by incident polarized light.

Virtually any polarized light source can be used to provide an analyzer for cards treated as above. Probably the simplest, however, is a substantially transparent light polarizer, many of which are well known, a polarizing sunglass, for example. If the cards of this invention are simply viewedthrough such a device, one of the two component colors will be observed, depending upon whether the vibration direction is parallel or perpendicular to the orientation direction of the polarizing portion of the card overlay; when the analyzer is rotated through 90, the remaining component color is rendered apparent.

In order to avoid the necessity of continuously rotating the analyzing device in examining cards for authenticity in accordance with the instant invention, it is particularly convenient to employ a split-field polarizer, that is, a planar light polarizing element comprising two sections joined together in the same plane, the vibration direction of one section being perpendicular to that of the other.

The operation of dichroic dye light-polarizing areas incorporated into laminations comprising identification cards, credit cards, and the like, in accordance with this invention will be readily understood by referring to the accompanying drawings.

FIGURE 1 represents a polarized light analyzer comprising a split-field planar light-polarizing device. Such a device may comprise any of the many known and commercially available light-polarizing materials, such as iodine-containing molecularly oriented polyvinyl alcohol, cellulose-based polarizers, or even two Nicol prisms appropriately fused together. It may also comprise a dichroic dye polarizer. (The color of such a dyedmaterial will obviously atect the visual appearance ot" the laminations viewed through it; however, the distinctiveness of the various colored components will be readily apparent to the viewer notwithstanding.) As shown in FIGURE 1, the upper half 8 of the polarizer has a vibration direction, indicated by the position of thearrows, which is perpendicular to that of the lower portion 9.

Obviously, in actual use, the analyzer may be positioned in any manner desired; however, for purposes of illustration in the remaining gures to be explained below, it will be assumed that in each instance, the analyzer is positioned as shown in Example l.

FIGS. 2 through 8 represent a series of identification cards, each of which has laminated thereto a substantially transparent, molecularly oriented overlay containing a particularly dyed stripe, and each of which has super' posed thereon an analyzer as described above. In each of the cases represented by these figures, the orientation direction of the molecules of the plastic overlay is vertical,

and parallel to the dyed stripe.

FIG. 2 represents a' card 10 having an overlay containing a stripe formed of a single, positive dichroic dye. To the naked eye, such a stripe will have a given color, blue, for example, indicated at the upper and lower portions 12 of the stripe. When viewed through analyzer 11, the color in the upper portion 13 is substantially reduced or eliminated altogether, in accordance with the principles of positive dichroism previously discussed; the color in the lower portion 14 is somewhat intensified by the inherent darkening effect of the light-polarizing analyzer, for example, to a deeper blue.

FIG. 3 represents a lamination similar to that of FIG. 2, except that the dyed stripe is formed of a negative dichroic dye of a given color, yellow, for example, indicated at the upper and lower portion 15 of the stripe. When viewed through analyzer 11, however, the effect is just the opposite of that shown in FIG. l; that is, the color in the lower portion 17 of the analyzer is substantially reduced or eliminated, while the color observed through the upper portion 16 of the analyzer appears l more intense, for example, as a deeper yellow.

FIG. 4 represents a lamination within the scope of this invention, similar to those of FIGS. 2 vand 3, except that the dyed stripe comprises a mixture. of a positive dichroic dye, and a negative dichroic dye of a different color. Fo'r purposes of illustration, it will be assumed that the particular dyes employed are similar in color to those mentioned in connection with FIGS. 2 and 3, that is, a blue positive dichroic dye and a yellow negative dichroic dye. To the naked eye, as shown at the upper and lower portion 18 of the stripe, such as a stripe would exhibit the color achieved by a mixture of blue and yellow, namely, green. However, when viewed through analyzer 1l, the mixture is broken into its color components in accordance with the principles given above. Thus, the color observed through the upper portion 19 of the analyzer will be yellow; thecolor observed through the lower portion 20 will be blue.

FIG. 5 represents a lamination similar to that of FIGS. 2 and 3, except that the dyed stripe is formed of an isotropic, i.e., non-dichroic dye of a given color. When viewed through analyzer 11, the colors observed in both the upper portion 22 and lower portion 23 are identical, and are substantially identical to the color of the stripe 12 as seen to the naked eye, except that they may be somewhat darker or deeper in intensity, owing to any light-decreasing etect of the analyzer itself.

FIG. 6 represents a lamination within the scope of the invention, similar to those of the foregoing tigures, except that the dyed stripe comprises a mixture of a positive dichroic dye and an isotropic dye; for purposes of illustration, it will be assumed that the positive dichroic dye is blue in color, and the isotropic dye, yellow. To the naked eye, as represented by the upper and lower portions 24 of the dyed stripe, the color 'observed is green. When observed through analyzer 11, however, while the lower portion 26 will exhibit a darker or more intense green, in the upper portion the color of the positive ichroic dye will be substantially excluded, and the color observed will be not green, but yellow.

FIG. 7 represents a lamination within the scope of this invention similar to that of FIG. 6, except that the dyed stripe comprises a mixture ofa negative dichroic dye and an isotropic dye; for purposes of illustration, it will be assumed that the negative dichroic dye is red in col-or, and the isotropic dye, yellow. To the naked eye, as represented by the upper and lower portions 27 of the dyed stripe, the color is orange. When viewed through analyzer v11, however, while the upper portion 28 will exhibit a darker or more intense orange, in the lower portion 29,

the color of the negative dichroic dye will be substantially excluded, and the color observed will not be orange, but yellow.

FIG. 8 represents a lamination within the scope of this invention similar to that of the foregoing figures, except that the dyed stripe comprises a single double dichroic dye of a given color, violet for example. To the naked eye, as represented by the upper and lower portions 30 of the stripe, only the violet color is observed. When viewed through analyzer 11, however, two separate and distinct colors are observed in areas 31 and 32, tan and blue, for example.

The' pol'arizer-containing overlay for lamination to information-bearing cards or the like in accordance with this invention may comprise any molecularly oriented, substantially transparent material which is dyeable with dichroic dyes, such as oriented polyvinyl alcohol, polyvinyl alcohol-polyvinylene, cellulose, or glass. The dyes are applied to such materials in accordance with techniques well known to the art of vectography.

Where the dyed area of the overlay is a stripe as shown in the accompanying drawings, one convenient way for applying the dye is to provide a dye solution comprising the desired dye mixture or single double-dichroic dye, and further, providing an absorbent wick of felt, sponge, or the like. One end of the wick is allowed to remain in the dye so'lution and the other, allowed to protrude from the dye bath in such a way that the film to be dyed can be passed or propelled over and in Contact therewith. The free end of the wick thus paints a continuous stripe on lthe tilm. It will be obvious that if such an arrangement is used, where the bath comprises a mixture of dyes, the concentrations of the ingredients, solvents, working temperatures, pH, etc., must be adjusted in accordance with well-known chromatographic techniques so as to insure that both dyes are absorbed by the wick at about the same rate.

The intensity of the dyed area can be as high or low as desired, and can readily be controlled by varying such .a yi

7 factors as the concentration of the dyes, dyeing temperature, dyeing technique, etc. lt will be obvious, however, that where the overlay is used for printed informationbearing cards, the dyed area should be intense enough to render the various colors and the components thereof readily apparent, but it should not be so dark as to obscure the printed indicia. Thus, the actual intensity of the area will depend in part upon the particular color, a very intense yellow, for example, being satisfactory while darker colors, such as brown or black would have to be considerably lighter.

One technique for providing dyed areas of relatively hign intensity at room temperature where the molecularly oriented material is polyvinyl alcohol is to treat the oriented sheet prior to dyeing with a caustic solution, such as a solution of sodium hydroxide. This and other techniques for enhancing the dye receptivity of the sheet are fully described in US. Patent No. 2,892,382, issued to William H. Ryan and Vivian K. Walworth on June 30, 1959.

Where the dyed overlay material comprises polyvinyl alcohol, it has also been found advantageous to harden or cross-link it subsequent to dyeing, to prevent any lateral diffusion of the dyes. A simple means of achieving this is to wash the dyed surface prior to lamination with a solution of a suitable cross-linking or hardening agent, such as boric acid. This and other techniques for hardening the dyed sheet are fully described in U.S. Patent 2,996,956, issued Aug. 22, 1961, to William H. Ryan and Howard C. Haas, and No. 3,058,393, issued Oct. 16, 1962, to William H. Ryan and Leonard C. Farney.

If desired, the dyed area may have a given contiguration in the overlay, so as to comprise a distinctive shape, insignia, word, etc. In such a case, the dye or dyes selected would be printed directly onto the oriented plastic overlay in accordance with well-known vectographic procedures. Where dichroic dyes are printed onto molecularly oriented polymeric overlays, as opposed to being painted on as described supra, it is generally necessary to enhance the dye receptivity of the overlay sheet by mercerization with sodium hydroxide as described above, or by using7 other known vectograph mordanting procedures.

The manner in which the transparent polarizing overlays are laminated to the information-bearing surface will depend in part upon the particular polarizing material selected and in part upon the nature of the surface to which it is being applied. For example, where the information-bearing surface comprises metal, paper, wood, or a wood product, any one of numerous commercially available pressure-sensitive adhesives, such as those based on butadiene-acrylonitrile copolymers may lbe applied to either the polarizer surface or the information-bearing surface, following which the two surfaces are pressed together. Alternatively, epoxy-based adhesives may be ernployed in bonding the surfaces. It should be borne in mind, however, that certain of the commercially available epoxy adhesives require the application of heat for the provision of a good adhesive bond; where such an adhesive is ernployed, care must he taken not to apply heat of such a degree that it will dis-orient the polarizing material or otherwise render its polarizing characteristics non-uniform.

As indicated above, the present invention is especially well-suited to use in connection with identification cards or badges, which cards or badges frequently comprise photographic likenesses of their holders or bearers, togcther with other identifying indicia. Conventional photographs, the surfaces of which are generally gelatin or modied gelatin, may be affixed to polarizer-containing overlays with the aid of a transparent, pressure-sensitive adhesive such as Kleenstik adhesive (commercially available from National Starch and Chemical Corporation, Newark, NJ.) or epoxy resins; of particular ellicacy in thisrespect arc polymeric adhesives such as Eastman 910 8 cement, a cyano-acrylate polymer, commercially available from Armstrong Cork Company, Lancaster, Pa.

Where the identification card or badge contains a photographic likeness of its holder, it is often desirable, in the interest of speed and efficiency, to provide a rapid means of obtaining such a likeness. Of particular advantage in this respect, where a blaclt-and-white photographic image is sought, are silver transfer images of the type which may be produced by applying a processing composition containing a silver halide developing agent and a silver halide solvent to a photoexposed photosensitive silver halide element and an image-receptive element that are in superposed relation. The processie." composition acts to reduce exposed-silver halide to silver, to react with unreduced silver halide to form a water soluble, complex silver salt, and to transfer it to the image-receptive element, and there, reduce it to silver. Examples of photographic materials useful in the production of the foregoing type of photographic silver images are described in detail in US. Patent No. 2,543,181, issued in the naine of Edwin H. Land on Feb. 27, 1951, and in U.S. Patent No. 2,647,056, issued in the name of Edwin H. Land on July 28, 1953. ln a typical process employing such materials a processing composition containing a viscous aqueous solution of a silver halide developing agent, a silver halide solvent and an alkali is spread in uniformly thin layer between the superposed surfaces of the photoexposed gelatino silver halide stratum of a photoscnsitive element and the silver-receptive stratum of an image-receptive element The elements are mainte-.ined in superposed relation for a predetermined period ordinarily of approximately 10 to 120 seconds in duration, during which exposed silver halide is reduced to silver and unreduced silver halide forms a water soluble, complex silver salt which diffuses through the layer of composition to the image-receptive stratum, where, upon being reduced to silver, it forms a silver print. At the end of this period, the photosensitive element, preferably together with the solidified layer of processing composition, is stripped from the image-receptive element.

Image-receptive strata of the foregoing type include silver precipitating nuclei dispersed in a macroscopically continuous vehicle comprising sub-macroscopic agglomerates of minute particles of a water insolule inorganic, preferably siliceous material such as silica aerogel. Silver grains precipitated in the foregoing manner are concentrated primarily at the surface of the stratum. This stratum, both before and after receiving these precipitated silver grains, is extremely thin, preferably being approximately 1 to 8 microns thick. Materials of the foregoing type are specifically described in U.S. Patents Nos. 2,698,237 and 2,698,245, issued to Edwin H. Land on Dec. 28, 1954- The foregoing process is particularly adapted for use in a Polaroid Land camera made by Polaroid Corporation, Cambridge, Mass. 02139, or a similar camera structure such, for example, as the camera forming the subject matter of U.S. Patent No. 2,435,717, issued to Edwin H. Land on Feb. 10, 1948.

Where photographic likenesses of individuals are desired for identification card purposes, the foregoing process when used in cameras of the aforementioned type renders it possible to obtain such likenesses immediately uopn making the photographic exposure, and obviates the the necessity of the usual waiting period required for conventional photographic processes wherein a negative must be photoexposed and developed in a separate subsequent operation.

Silver transfer prints of the aforementioned type can be affixed to any of the previously described polarizing materials by way of a pressure-sensitive adhesive. It is also possible, however, to laminate such prints to certain polarizers in a security seal, that is, a seal which cannot be broken or tampered with without immediately clearly rendering obvious the intrusion by destroying or detacing the photographic likeness. T-hus, not only is the surface of the lamination protected from intrusion by the polarizer, but also, the lamination cannot be separated from behind without being easily detected. In one type of security seal for such prints, the polarizer comprises a hydroxylated polymer such as polyvinyl alcohol or polyvinyl alcohol copolymers, or hydrolyzed cellulose acetate, and is laminated to the transfer print by way of an interlayer which comprises `a copolymer of vmethyl vinyl ether and maleic anhydride.

Methods for preparing security-sealed laminations as just described are set forth in copending U.S. patent application, Ser. No. 562,767 of Howard C. Haas, filed July 5, 1967.

In certain instances it is desirable to provide an identication card or lbadge comprising a color photographic likeness of its holder or wearer and at the same time, retain the eiiiciency in production of the silver transfer prints described above. Color photographs of this nature can be prepared by diffusion transfer processes, wherein a sheet of photosensitive material is exposed to create therein `a latent image. The latent image is developed and, concurrent with an under the control of this development, an imagewise distribution of color-providing materials is formed. At least a portion of these color-providing materials is transferred by means of an alkaline aqueous processing liqnid to a superposed image-receiving layer to form a colored positive image thereon. As examples of such processes, mention may be made of the processes claimed `and disclosed in U.S. Patent No. 2,983,606, issued May 9, 1961 to Howard G. Rogers wherein dye developers (i.e., dyes containing a silver halide developing function and capable of developing exposed silver halide) are the color-providing materials; the processes claimed `and disclosed in U.S. Patent No. 2,647,049, issued July 28, 1953, to Edwin H. Land, wherein color developersare employed to develop the latent image and color couplers are the color-providing materials; and the processes disclosed in U.S. Patent No. 2,774,668, issued Dec. 18, 1956, to Howard G. Rogers, wherein complete, preformed dyes which are capable of coupling are used as the color-providing substances.

The image-receiving elements used in such processes generally comprise an opaque or tr-ansparent support coated with an image-receiving layer of a dyeable material which is permeable to the alkaline aqueous processing solution. The dyeable material generally comprises a film-forming material such as polyvinyl alcohol, and polyvinyl yalcohol-polyvinyl pyridine. The image-receiving layer may also include other materials useful in diffusion transfer processes, such as dye mordants, antifoggants, oxidizing agents, and acids and alkalies for pH adjustment.

Image-receiving elements of the foregoing type are described in U.S. Patent No. 3,148,061, issued Sept. 8, 1964 to Howard C. Haas, and the aforementioned U.S. Patent No. 2,983,606.

In -accordance with the present invention, color photo graphs of the aforementioned type may be affixed to any of the polarizing materials previously described via commercially available pressure-sensitive adhesives. Where the particular polarizing material selected comprises a polyvinyl alcohol-based polarizer, it is also possible to provide a security-sealed lamination by simply wetting the diffusion transfer color print, either with water or.

with water containing dissolved polyvinyl alcohol as a dope, or by employing a freshly' prepared Adiffusion transfer color print whose surface is still wet from photographic processing and pressing the face of the print di rectly against the surface of the polarizer. Processes for preparing security-sealed diffusion transfer color photographs are disclosed and claimed in copending U.S. patent application of Robert L. Malster, Ser. No. 451,705, led Apr. 29, 1965.

It will be appreciated that the information-bearing surfaces are not limited to those described previously, but may comprises virtually -any material which is capable of being printed on Or otherwise impregnated with any desired data. Care must be taken, however, where the surface comprises a synthetic resinous material to select an adhesive bond, or interlayer which forms a good bond not only to the polarizer Ibut to the particular information-bearing surface as well.

Where laminations of the aforementioned types are employed as so-called credit cards, it is often desirable that the final card be embossable with certain information, such as with the holders name, address or code number. These embossed cards may be placed in a small imprinter whereby the embossed indicia are applied .to a receipt form or the like. Such cards are generally termed self-writing since they eliminate the time that would Lbe required to manually imprint the necessary indicia on the receipt form. Embossed or embossable cards may be prepared which incorporate a light-polarizing element and which are thus provided with the security feature described above. Such cards preferably comprise a liexible information-bearing layer such as paper or a photo-graph, to which is bonded a flexible light-polarizing element, such as a polyvinyl alcohol-based polarizer. An additional transparent layer is then bonded to the surface lamination, which comprises a synthetic material capable of providing stable, sharp-edge raised letters or numerals as a result of a suitable embossing procedure, the techniques for which are well known to the art. Synthetic films of the aforementioned nature are conventionally known as rigid vinyl or semi-rigid vinyl, and generally comprise polyvinyl chloride, or blends or copolymers of polyvinyl chloride and polyvinyl acetate.

It will lbe appreciated that the use of transparent nonpolarizing films laminated over the polarizing element to polarizer-protected information surfaces is not limited to those instances wherein an embossable lamination is desired. Such a technique can be employed whenever it is sought to further protect the information-bearing surface; the transparent nonpolarizing film may comprise any substantially transparent material, such as synthetic resins such as polystyrene, or glass, depending in part upon the desired flexibility of the final protected lamination.

The following nonlimiting examples provide specific illustrations of identification cards protected with dichroic dye polarizers in accordance with this invention.

Example 1 A dye bath was prepared comprising 30.0 g. of Acid Blue 170 (trade name Cibalan Blue BLR), a negative dichroic dye, and 2.0 g. of Direct Red 117, color index 28230 (trade name Diazamine Light Red 7B), a positive dichroic dye, dissolved in 600 cc. of watenA felt wick, measuring about 8 inches in length and about 3/8 inch in width, was suspended in such a way that its lower end was in the dye bath. A sheet of polyvinyl alcohol, oriented `by stretching to four times its original length and backed with a support comprising cellulose acetate butyrate and intermediate layers comprising cellulose nitrate and cellulose nitrate/hydrolyzed polyvinyl alcohol, was passed over and in contact with the upper end of the wick at a rate of about 3 feet per minute and a temperature of about 160 F., resulting in a violet stripe about 3A; inch wide on the polyvinyl alcohol sur face. The dyed surface was washed "with a 1% aqueous solution of lboric acid and vacuum dried at room temperature. Thereafter, the same surface was coated at room temperature with a 1% solution of polyvinyl alcohol, and dried.

A diffusion transfer color photographic image was made using Polaroid Polacolor Land Film, Type 108, and a Polaroid Automatic Model camera. The imagereceptive layer together with its superposed photosensi- 1l tive element was pulled from the cantera; the elements were maintained in superposed position for about sixty seconds, after which they were stripped apart. Immediately after stripping, while the image-receiving surface was -still fresh and wet, it was pressed firmly against the polyvinyl alcohol surface of the dyed overlay prepared as above, and the excess overlay trimmed away. After a period of about minutes, an attempt was made to separate the lamination; it was found that the image layer adhered rmly to the overlay in a security seal.

As indicated above, the stripe which resulted across the photograph appeared to the naked eye to be violet in color. The stripe was then observed through a neutral color linear polarizer having a transmission of about 38%, commercially available from Polaroid Corporation, Cambridge, Mass. 02139, as rType HN 38 sheet, placed in such a way that its vibration direction was parallel to the direction of orientation of the stretched polyvinyl alcohol; the color of the stripe so observed was red. The'sarne polarizer was rotated through 90, during which the color of the stripe was observed to change to violet and then finally to blue. `vVhen the same stripe was observed through a split-'held polarizer made from the same Type HN 38 sheet and oriented with respect to the lamination as shown in FIG. 2 through 8 described above, the upper portion ofthe stripe appeared red and provided a sharp contrast with the lower portion thereof, which appeared blue.

The coating of polyvinyl alcohol which was applied to the dyed polyvinyl surface of the overlay prior to its lamination to the photographic print was included for the purpose of insuring complete uniformity of the security seal Abetween the overlay and the photographic image; substantially the same effect is obtained if the image surface of the photograph or the overlay itself is wetted with an aqueous polyvinyl alcohol solution as a dope immediately prior to lamination. However, neither procedure is mandatory; satisfactory laminations were also prepared by following the foregoing procedure, but omitting the extra polyvinyl alcohol coating altogether. Y

Polyvinyl alcohol lms backed with cellulose acetate butyrate via intermediate layers of cellulose nitrate and cellulose nitrate/hydrolyzed polyvinyl alcohol may be prepared in accordance with the teachings contained in U.S. Patent No. 2,362,580, issued Nov. 14, 1944 and 2,- 541,478, issued Feb. 13, 1951, to Gale F. Nadeau and Clemens B. Starck, and U.S. Patent No. 2,835,609, issued May 20, 1958 to Clemens B. Starck, Gale F. Nadeau, and Carl F. Smith.

EXAMPLE 2 The procedure of xample 1 was followed using the same materials except that the dye bath comprised 5 1g. of Acid Yellow 152 (trade name Calcofast Neutral Yellow 3R"), a negative dichroic dye, and 1.5 g. of Direct Blue-l, color index 24410 (trade name Niagara Sky Blue 6B), a positive dichroic dye, dissolved in 200 cc. of water and 50 cc. of ethanol. The stripe in the resulting lamination was given to the naked eye. When observed through the same neutral polarizer as was employed in Example 1 placed in such a way that its Vibration direction was parallel to the direction of orientation of the stretched polyvinyl alcohol, the stripe color was noted to appear deep blue. When the same polarizer was rotated through 90, the color of the stripe was observed to change from blue to green to a clear golden yellow. When the same stripe was observed through the splitfield polarizer employed in Example 1 and oriented as described therein, the upper portion thereof appeared blue, providing an excellent sharp contrast to the lower portion, which appeared yellow.

EXA MPLE 3 The procedure of Examples l and 2 was followed using the same materials, except that the dye bath comprised 37.5 g. of Acid Yellow 152, the same negative dichroic dye as was used in Example 2, and 2.5 g. of Direct Red 117, the same positive dichroic dye as was used in Example 1, dissolved in 500 cc. of water and 100 cc. of ethanol. The stripe in the resulting lamination was orange to the naked eye. When observed through the same neutral polarizer as was employed in Examples 1 and 2, placed in such a way that its vibration direction was parallel to the direction of orientation of the stretched polyvinyl alcohol, the stripe color was noted to appear red. When the same polarizer was rotated through 90, the color of the stripe was observed t`o change from red to orange to yellow. When the same stripe was observed through the split-field polarizers employed in the foregoing polarizers employed in the foregoing examples and oriented as described therein, the upper portion thereof appeared red, providing an excellent sharp contrast to the lower portion, which appeared yellow.

The particular dyes to be employed in any given mixture will depend primarily upon the colors which are desired. As examples of other positive dichroic dyes which are useful in the practice of this invention, mention may be made of:

Name oi dye Color Index No. Other designation Direct Rod 3".. Direct Red 75. Direct Rod 81. Direct Violet 4 Direct Violet 8 Direct Yellow G Direct Yellow 7 Direct Yellow Direct Yellow Direct Yellow Direct Yellow 28 Direct Yellow 44 Direct Yellow l0 As additional examples of negative dichroic dyes which are useful in the practice of this invention mention may be made of:

Namo of dye Color Index No. Othordesignaticn Vat Blue-41 73040 Acid Brown-715 Acid Orange-60 Vat Orange 3 59300 Vat Orange 9 59700 Acid Rod 182 Prototype 501. Mordant, Rod 3 58005 Acid Violet, 70 Acid Violet Vat Violet 2 Vat Violet 17 o5 Acid Yellow 99 13900 Vat Violet 1 70600 Vat Violet', 2l 69705 While the color combinations which are obtainable with mixtures of positive and negative dyes may be somewhat restricted, the use of an isotropic dye along with either a positive or a negative dichroic dye renders the various possibilities limited only by the spectrum. Virtually any isotropic dye may be so employed, provided its nature is such that it will dye, or be taken up by, the particular oriented matrix employed.

As a few examples of diiierent colored isotropic dyes which are suitable for the last-mentioned purpose, mention may be made of:

Acid Blue 16l-(Color Index No. 15706) Basic Blue 4(C.l. 51004) Direct Blue 199 Acid Brown 45 Acid Green 57 Basic Orange 2l-(C.I. 48035) Acid Red 220 Acid Red 253 Mordant Violet l-(C.I. 43565) Acid Yellow 114 As noted above, certain dyes have been found to exhibit double dichroism by themselves. Thus, for example, it has been observed that if a piece of molecularly oriented polyvinyl alcohol sheet is stained with a dye commercially designated as Pilate Fast BlackWAN, to the naked eye, the color observed is deep violet. However, when the sheet observed through one portion of the polarizer is royal blue, the other, tan. As examples of other commercial dyes which have been observed to exhibit the same kind of double dichroism, mention may be made of Lannmid Brown RD Neolan Black WA Ortolau Brown 3R... Pilate Fast Black WAN.. Supralan Black NB Acid Brown 09 Acid Black Acid Binck 1o7 Vialon Fast Black R Similar to Acid Similar to Black 63. 12195. Vialon Fast Claret; R Acid Red 228 Identification cards, credit cards, and the like made in accordance with this invention can be slipped into a protectve pouch or envelope, at least one side of which is transparent so as to reveal the information-bearing surface and the dyed overlay laminated thereto. Where such an envelope or pouch is used, a portion of the transparent wall through which the information-bearing surface is viewed may comprise a split-held polarizer superposed over the dyed portion of the card itself, in such a way as to provide a built-in analyzer. The various colors employed together with all of the components thereof are thereby rendered simultaneously visible, without any ancillary device. Thus, not only are counterfeit badges readily ascertainable by virtue of the color scheme, but also, alterations to the lamination itself can be detected by the resutling discontinuity of light reiiected therefrom. v

It will be obvious that overlays used in accordance with the teachings contained herein need not have only a single dyed area, but may comprise a plurality of dyed areas of the same or different colors. For example, if desired, an identification card may be provided with an overlay having two dyed stripes of different colors each of which may comprise any of the dyes or dye combinations described above; such stripes may each comprise different dyes or dye mixtures, or if desired, may each comprise a first dye common to both stripes, along with a second dye which differs as between the two stripes.

While the foregoing description has generally been concerned with laminations of small dimensions such as identification or credit cards, it will be apparent that the.

same principles can readily be employed for the protection of larger information-bearing surfaces. Thus, if such a large surface, such as a printed page, has laminated thereto a substantially transparent molecularly oriented overlay at least part of which is stained or dyed in accordance with the teachings contained above, alterations thereto can be ascertained with the aid of an analyzer in a manner exactly as described for hidentification cards.

Since certain changes may be made in the above processes and products Without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A laminar structure comprising an informationbearing surface having aixed thereto asubstantially transparent sheet-like element at least -a portion of which is light-polarizing and which light-polarizing portion comprises an oriented plastic dyed with a composition elected from the group consisting of: (a) -mixtures comprising a positive dichroic dye and a negative dichroic dye of a color different from that of said positive dichroic dye with which said negative dichroic dye is mixed; (b) mixtures comprising a positive dichroic dye and an isotropic dye of a color different from that of said positive dichroic dye with which said isotropic dye is mixed; (c) mixtures comprising a negative dichroic dye and an isotropic dye of a color dierent from that of said negative dichroic dye with which said isotropic dye is mixed; and (d) double-dichroic dyes.

2. The structure as delined in claim 1 wherein said oriented plastic comprises molecularly oriented polyvinyl alcohol.

3. The structure as defined in claim 1 wherein said information-bearing surface comprises a photograph.

4. The structure as defined in claim 1 including a substantially transparent embossable vinyl film bonded to the outer surface of said substantially transparent sheet-like element.

5. The structure as dened in claim 4 wherein said information-bearing surface comprises a photographic image formed in polyvinyl alcohol.

6. A laminar structure comprising a rst layer which comprises a photographic image formed in polyvinyl alcohol; a second layer bonded to the image-bearing surface of said photographic print which comprises a substantially transparent sheet-like element comprising molecularly oriented polyvinyl lalcohol at least a portion of which is light-polarizing, which light-polarizing portion comprises a composition selected from the group consisting of mixtures comprising a positive dichroic dye and a negative dichroic dye of a color different from that of said positive dichroic dye with which said negative dichroic dye is mixed, mixtures comprising a positive dichroic dye and and an isotropic dye of a color dierent from thatl of said positive dichroic dye with which said isotropic dye is mixed, mixtures comprising .a negative dichroic dye and an isotropic dye of a color dif-ferent from that of said negative dichroic dye with which said isotropic dye is mixed, and double-dichroic dyes; a third layer comprising cellulose nitrate and hydrolyzed polyvinyl alcohol; a fourth layer comprising cellulose nitrate; Iand a fifth and outer layer comprising cellulose acetate butyrate.

'7. The structure as defined in claim 6 wherein said light-polarizing portion of said molecularly-oriented polyvinyl alcohol comprises a mixture of Acid Blue and Direct Red 117.

8. The structure as defined in claim 6 wherein said light-polarizing portion of said molecularly oriented polyvinyl alcohol comprises a mixture of Acid Yellow 152 and Direct Blue l.

9. The srtucture Ias defined in claim 6 wherein said light-polarizing portion of said molecularly oriented polyvinyl alcohol comprises a mixture of Acid Yellow 152 and Direct Red 117.

10. A polarizer-protected laminar structure comprising an information-bearing surface having afiixed thereto a iirst substantially transparent sheet-like element at least a portion of which is light-polarizing, which light-polarizing portion comprises a molecularly oriented polymer dyed With a composition selected from the group consisting of mixtures comprising a positive dichroic dye and a negative dichroic dye of a color different from that of said positive dichroic dye with which said negative dichroic dye is mixed, mixtures comprising a positive dichroic dye and an isotropic dye of a color different from that of said positive dichroic dye with which said isotropic dye is mixed, mixtures comprising a negative dichroic dye and an isotropic dye of a different color from that of said negative dichroic dye with which said isotropic dye is mixed, and double-dichroic dyes; and a second substantially transparent sheet-like element axed to said tirst element, which second element comprises a split-field light polarizer superposed on said light-polarizing portion of said rst element.

11. A polarizer-protected identification card comprising a laminar structure comprising a rst layer having an information-bearing surface, `and a second layer axed to said information-bearing surface of said informationbearing surface of said first layer, which second layer comprises a'substantiaily transparent sheet-like element at least a portion of which is light-polarizing, and which light-polarizing portion comprises a molecularly oriented polymer dyed with a composition selected from the group consisting of mixtures comprising a positive dichroic dye and a negative dichroic dye of a color different from that of said positive dichroic dye with which said negative dichroic dye is mixed, mixtures comprising a positive dichroic dye and an isotropic dye of a color different from that of said positive dichroic dye with which said isotropic dye is mixed, mixtures comprising a negative dichroic dye and an isotropic dye of -a different color from that of said negative dichroic dye with which said isotropic dye is mixed, and double-dichroic dyes; which laminar structure is contained in an envelope, the wall of said envelope adjacent t0 said second layer of said lamination being substantially transparent and being further characterized in that at least a portion thereof comprises a split-field light polarizer superposed on said lightpolarizing portion of said second layer of said lamination.

References Cisted v UNITED STATES PATENTS 2,331,575

EUGENE R. CAPOZO, Primary Examiner.

W. I. CONTRERAS, Assz'satnt Examiner. 

